391840 has 48 divisors (see below), whose sum is σ = 967680. Its totient is φ = 149760.

The previous prime is 391823. The next prime is 391847. The reversal of 391840 is 48193.

It is a zygodrome in base 4.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (391847) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4921 + ... + 4999.

It is an arithmetic number, because the mean of its divisors is an integer number (20160).

2³⁹¹⁸⁴⁰ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 391840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (483840).

391840 is an abundant number, since it is smaller than the sum of its proper divisors (575840).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

391840 is a wasteful number, since it uses less digits than its factorization.

391840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 125 (or 117 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 25.

The square root of 391840 is about 625.9712453460. The cubic root of 391840 is about 73.1761555510.

The spelling of 391840 in words is "three hundred ninety-one thousand, eight hundred forty".